The sun's thermal energy has been used for thousands of years to provide hot water and heat. Three major limitations of contemporary solar thermal systems prevent their widespread adoption as an alternative to fossil fuels: collector aesthetics, costs of the system (including collectors and installation), and limited functionality of the thermal collectors. One of the most significant barriers to adoption cited by architects, developers, and property owners is the unsightliness of current thermal collectors are that they are “boxed” so that they cannot be seamlessly integrated as part of the architecture or structure of a building. The construction of contemporary solar thermal collectors and the requirement that they be installed to obtain the best solar exposure, limits their installation mainly to the roofs of buildings, thus confining their area and thermal capacity.
Another barrier to adoption of current solar thermal technologies is their high cost. The high cost of the collectors can be attributed to the costs of raw materials (copper, aluminum, and stainless steel) and to the current production process of typical “plate and tubes” solar collectors, which uses labor-intensive techniques that are difficult to automate. The high costs of materials and labor motivate manufacturers to experiment with the use of less expensive plastic absorbers in flat-plate solar collectors. However, inexpensive plastic absorbers are unsuitable in glazed flat-plate solar collectors because of their low softening temperature. Some costly plastic materials are able to satisfy the temperature requirements for glazed flat-plate solar collectors, but the high cost of these plastic materials diminishes their advantage over metal absorbers. The high costs of installation of the solar thermal system results from treating the system as an add-in to the existing building structure. This requires the use of additional materials and labor to install the system.
Finally, the collectors function only as elements of the solar thermal system with no other structural or functional purposes. If the collectors are integrated into the external envelope of a building, doubling as a cladding system and covering a substantial part of the envelope, they can also limit solar gains to the building and dramatically lower the costs of cooling the building's interior. Additional benefits can be derived from the system if it can be used at night to dissipate excess of energy. The relative cost of the installation can be lowered if the solar collectors are used as structural elements of a building envelope or function as cladding, thus decreasing the cost of the system as a share of the overall cost of the building. The savings arising from less expensive materials, production methods, and installation would provide a stronger economic incentive for the use of solar thermal systems.
Despite their potential for energy conservation, contemporary solar thermal systems have remained mostly in separate domains from other thermal systems used in a building. The integration of these separate systems into a single comprehensive system built directly into the structure of a building can offer substantial monetary and energy savings.